a= input("是否退出程序（y/n)？")
while a !='y':
    height,weight=eval(input("请输入身高（米）和体重（公斤）[逗号隔开]:"))
    BMI=weight/pow(height,2)
    print("BMI数值为：{:.2f}".format(BMI))
    who,nat="",""
    if BMI<18.5:
        who,nat="偏瘦","偏瘦"
    elif 18.5<=BMI<24:
        who, nat="正常","正常"
    elif 24<=BMI<25:
        who,nat="正常","偏胖"
    elif 25<=BMI<28:
        who,nat="偏胖","偏胖"
    elif 28<=BMI<30:
        who,nat="偏胖","肥胖"
    else:
        who,nat="肥胖","肥胖"
    print("BMI指标为国际'{}',国内'{}'".format(who, nat))
    a=input("是否退出程序（y/n)?")



